Fix sidebar selection when jumping with Cmd-number

[brooksc]

Problem

When a task is selected with the mouse, the sidebar keeps focus and renders the selection outline from sidebarFocusedTaskId. Using Cmd-1 through Cmd-9 changed the active task, but left sidebarFocusedTaskId pointing at the last mouse-selected row, so the outline stayed on the wrong task.

Fix

Update jumpToTask() so Cmd-number jumps also synchronize the sidebar focused task when the sidebar currently owns focus. The change clears project focus and moves the sidebar outline to the jumped task.

Verification

• npm run check
• npm test
• Confirmed the PR branch contains one commit on top of latest johannesjo/main, touching only src/store/navigation.ts and src/store/navigation.test.ts.